The present invention relates to current regulators. More specifically, the present invention relates to current regulator having low voltage detection capability.
Electronic devices such as televisions and digital video disc players have become standard household accessories. These devices may be controlled directly or indirectly. For example, one may adjust the volume from a television by directly pressing on the xe2x80x9cVolume+xe2x80x9d button of the television. Alternatively, one may use the remote controller that comes with such television to indirectly adjust the volume. To do so, one presses on the xe2x80x9cVolume+xe2x80x9d button of the remote controller. In response, the remote controller generates an optical radiation signal and transmits such signal to the television. More specifically, a light emitting diode (LED) of the remote controller emits such signal so as to instruct the television to increase its volume. Within such controller, two AAA batteries may be installed to provide electric energy so as to produce a current to drive the LED.
Therefore, in applications in which a power supply provides a current to drive a load, it is desirable to prolong the life of the power supply. In addition, it is also desirable to detect when the electric energy of the power supply is low and thereby provides a signal indicating such status of the power supply so as to alert a user or operator. Furthermore, it is also desirable to detect whether the load has been dislodged so that corrective action can be taken.
According to one aspect of the present invention, a circuit for regulating a current provided by a power supply to drive a load in response to an input signal, is provided. The circuit contains a current source that has a specified current value and is coupled to the power supply. In addition, the circuit also comprises a controller that generates a reference voltage and is coupled to the current source. Furthermore, the circuit also includes a comparator that compares the reference voltage and a voltage at a node. To this node, controller is coupled. In addition, the load is coupled between the node and the power supply. In response to the input signal, the controller provides the current to drive the load. This current has a first current value that is proportional to the specified current value of the current source when the voltage at the node is greater than the reference voltage and a second current value that is based on the power supply when the voltage at the node is less than the reference voltage. Alternatively, this circuit may be modified so as to detect when [1] the power supply is low, [2] the load has been dislodged or [3] both.
According to a second aspect of the present invention, a method of regulating a current provided by a power supply to drive a load in response to an input signal, is provided. First, a current source having a specified current value is provided. Second, a reference voltage is provided. Third, comparing the reference voltage and a voltage at a node. With respect to this node, the load is coupled between the power supply and such node. Fourth, the current to drive the load is outputted in response to the input signal. This current has a first current value that is proportional to the specified current value of the current source when the voltage at the node is greater than the reference voltage. When the voltage at the node is less than the reference voltage, the current has a second current value that is based on the power supply.
These and other features and advantages of the present invention will be apparent from the figures as fully explained in the Detailed Description of the Preferred Embodiments.